1. Field of the Invention
The present invention relates generally to press brakes and, more particularly, to devices that vertically adjust the position of a die in a press brake to ultimately deform a workpiece such that the configuration of end portions of the workpiece are consistent with the configuration of a mid-portion of the workpiece.
2. Background of the Prior Art
It is common practice to use an adjustable bolster between a die and a press bed of a press brake to vary the crown or elevation of the die to obtain consistent bends and angles such that end and mid-portions of a workpiece have the same configurations after the workpiece is bent by a press brake. The adjustable bolster is required to compensate for the downward deflection or "yawning" in the press bed of the press brake caused by excessive use and operating loads. Further, the design of the press brake will influence workpiece inconsistencies and form an incomplete bend or "flat spot" due to deflection of the press bed. The greater the longitudinal dimension of the press bed, the greater the downward deflection in the press bed and the more pronounced the flat spots in the workpiece after operation of the press brake.
Prior art devices utilize a plurality of wedges to ultimately elevate the die to eliminate flat spots. An example of this technique is disclosed in U.S. Pat. No. 4,736,612. The patent teaches the use of multiple bolts and nuts to position each individual wedge members at a respective lateral position to elevate a corresponding wedge section thus positioning a predetermined portion of a die holder member.
One problem with this method of positioning the die holder is that an excessive amount of time is required to rotate all the adjusting bolts and thereby set all the wedges of the device for operation in the press brake, especially with some press brakes having press beds that are twelve feet in length. Another problem is that the initial cost of the device is excessive due to the large quantity of components which correspondingly causes increased time and expense for maintenance and replacement of parts. Still another problem is that time consuming observations and calculation are required to determine the distance each wedge has laterally traveled from its neutral position and the corresponding elevation differences in each of the wedges. Yet another problem is that the elevation of individual wedges reduces the space between the top of the device and the press brake thus limiting the vertical dimension of the die and workpiece.
Another prior art device utilizing a plurality of wedges is disclosed in U.S. Pat. No. 4,898,015. This patent teaches the use of two longitudinal wedges that are forced laterally apart to elevate a die holder set upon the wedges.
The problem with this device is that the dimensioning of the two wedges must be identical to avoid skewing the surface of the die holder which correspondingly "twists" the die and workpiece therein. Another problem is that once the two dies are laterally spaced apart, it is difficult to return the dies to their original positions where adjacent side walls of the wedges become congruently engaged and coplanar with the longitudinal centerline of a recess directly above the engaged side walls in the die holder.
Another problem that pertains to both the aforementioned patents, is that the wedges are forcibly positioned by threaded bolts that insert into bolt receiving orifices in the side walls of the wedges. The wedge side walls have relatively small lateral dimensions compared to the upper and lower surfaces of the wedge. The side wall lateral dimension limits the diameter of the bolt receiving recess therein. This may result in the wedge becoming permanently "bowed" due to extensive use and/or due to the large deforming force being focused upon a relatively small amount of metal which "stretches" the metal beyond its resiliency limits. Deforming the wedge via the wedge's upper surface, avoids permanent bowing and allows the wedge to continually return to a lineal position.
A need exists for a compensation device for a press brake die that includes one wedge having one inclined upper surface with a relatively large recess in the upper surface that receives a member therein that forcibly deforms or bows the wedge by rotating one adjustment bolt.